## https://yukicoder.me/problems/no/2229

MOD = 998244353

def main():
    H, W, K = map(int, input().split())
    xyv = []
    for _ in range(K):
        x, y, v = map(int, input().split())
        xyv.append((x, y, v))

    answer = 0
    for x, y, v in xyv:
        ans = x

        ans0 = ((x - 1) * x) % MOD
        ans0 *= pow(2, MOD -2, MOD)
        ans0 %= MOD

        d = max(0, x - y)
        ans1 = (d * (d + 1)) % MOD
        ans1 *= pow(2, MOD - 2, MOD)
        ans1 %= MOD
        ans += (ans0 - ans1) % MOD
        ans %= MOD

        
        d = max(0, x - (W + 1 - y))
        ans2 = (d * (d + 1)) % MOD
        ans2 *= pow(2, MOD - 2, MOD)
        ans2 %= MOD
        ans += (ans0 - ans2) % MOD
        ans %= MOD

        answer += (v * ans) % MOD
        answer %= MOD
    print(answer)

    



                


                



    


        




if __name__ == "__main__":
    main()